The invention relates to an internal combustion engine with at least one adjustable inlet valve.
Internal combustion engines with throttle-free load control are known in the art. In these known designs all inlet valve drives include an electromagnetic actuator and are controlled in a stepless fashion.
DE 43 41 945 A1 further discloses an internal combustion engine with at least two inlet valves, wherein one inlet valve is employed as the main inlet valve and one inlet valve is used as an additional inlet valve. The main inlet valve is operated by a camshaft via a motion transmitting member. The additional inlet valve is operable by a controllable operating mechanism by way of which the valve lift and/or the timing for the opening and the closing of the valve is adjustable. The main valve and the additional valve have different degrees of adjustment.
It is the object of the present invention to provide an internal combustion engine and a method for the operation thereof wherein, inspite of an essentially throttle free load control, the design expenses and the required space are relatively small.
In an internal combustion engine including cylinders with inlet and outlet valves, a first inlet valve drive having a first degree of adjustability for operating an inlet, valve of at least one cylinder and a second inlet valve drive having a second degree of adjustability for operating an inlet valve of the at least one cylinder, the engine includes other cylinders having inlet valves with inlet valve drives having only the second degree of adjustability for operating the inlet valves of the other cylinders.
With the arrangement according to the invention, an essentially throttle-free load control can be achieved and the design expenditures, the construction space requirements, the weight, the energy requirements and the costs can be relatively low. In percentage values, the degree of adjustment may vary between zero percent, that is, non-adjustable, and 100%, that is, steplessly adjustable; for example, with a particular valve drive the valve opening and closing timing may be steplessly adjustable; with another inlet valve drive, particular predetermined valve opening and closing times with given timing steps may be provided and with another valve drive the opening and closing times may not at all be adjustable.
If the inlet valve drive with the first degree of adjustability and the inlet valve drive with the second degree of adjustability are provided for one particular cylinder, a high degree of flexibility and an advantageous uniform loading of the internal combustion engine can be achieved.
If the inlet valve drive with the second degree of adjustability can be disabled energy can be saved by the disabling and, on the other hand, particularly in the lower partial load operating ranges, an advantageous throttle-free load control can be achieved.
The inlet valve drives can be formed by various mechanisms, which appear reasonable to an expert in the field. The inlet valve drives may include for example controllable camshafts. It is however advantageous if at least one inlet valve drive, particularly the inlet valve drive having the higher degree of adjustability includes an electromagnetic actuator. With electromagnetic actuators a high degree of adjustability can be achieved in a simple manner.
If at least one inlet valve drive, particularly an inlet valve drive with a low degree of adjustability, is at least partially part of an outlet valve drive, for example, in that one or several inlet valves are operated by a camshaft which, at the same time, operates outlet valves, a number of components, space, weight and expenses can be saved.
In other embodiments of the invention at least one cylinder may be provided with a throttle valve and for at least one cylinder the ignition timing may be adjustable, particularly in cylinders with inlet valve drives which have a low degree of valve adjustability. In certain transition areas, the enabling and disabling of inlet valve drives and/or cylinder groups may advantageously be controlled so as to prevent undesired gas flows. Furthermore, rapid load changes can be realized in a simple manner if at least for certain cylinders the ignition timing is adjustable.
Various combinations of the inlet valve drives with different degrees of adjustability may be provided. A solution which, based on design, expenditure and construction volume, is particularly advantageous is achieved with an internal combustion engine which includes a primary cylinder group whose cylinders have each at least a steplessly adjustable inlet valve drive with the first degree of adjustability and at least one inlet valve drive, which can be disabled, and which has a second degree of adjustability which is lower than the first degree of adjustability, and the internal combustion engine includes a secondary group of cylinders, which can be switched inoperative.
With such an internal combustion engine, advantageously in a first load range, only the inlet valves with the first degree of adjustment of the primary cylinder group are activated and, in a second higher load range, the inlet valve drives with the second degree of adjustment of the primary cylinder group can be additionally activated. In a third still higher load range, the secondary cylinder group can be activated. Within the load ranges, the load can be controlled to a large-extent by the inlet valve drives of the first degree of adjustment of the primary cylinder group.
The invention and its advantages will become more readily apparent from the following description of a preferred embodiment thereof on the basis of the accompanying drawings: